Thursday, October 14, 2010

Fall haze is upon us

We have officially crossed the meteorological brink from summer into fall. There is insufficient solar heating this week to build a convective boundary layer (CBL) that extends to crest level (~700 mb). The sounding from Tuesday afternoon shows a nicely developed CBL, but it tops out at about 775 mb.

CBL development yesterday was even more pathetic as slight warming above the surface kept it capped off at just above 850 mb.

Haze was quite apparent both afternoons, although DAQ observations from Hawthorne Elementary School suggest PM2.5 levels remain well below ambient air quality standards.

Nevertheless, as a caveman would put it, we are moving quickly from "ridge good" to "ridge bad" territory.  What's unfortunate is that we could use some storms now for SOLPEX and some ridging in December for PCAPS.  On the otherhand, as discussed in an earlier post,  a dry October is good for skiers.


  1. great blog Jim! Since temperature have been above average and there has been a lot of solar radiation with the recent ridging I was thinking these conditions are perfect for SOLPEX. Obviously there won't be any events now, but when the real troughs come in November and December there will be a greater vertical temperature gradient with a warmer than normal lake. Is there any product that looks at Great Salt Lake temperature anomalies?

  2. I'm hoping these conditions will ultimately prove good for SOLPEX, although I'm not sure I want the first IOP to be a "big one!"

    With regards to surface temperatures of the Great Salt Lake, the first thing you might want to check out is Crosman and Horel (2009, Remote Sensing of Environment). If you want real-time data, there are a few options, but I'm not sure how accessible any of them are. Erik used to maintain a page that provided the AVHRR-derived lake temperature. There is now also a buoy that the USGS has on the lake. Finally, Trevor has a technique for estimating lake temperatures, which I believe he is using in the WRF runs.

    I'll let Erik and Trevor perhaps comment and provide up-to-date information.

  3. We will have 5-day average AVHRR lake surface temperature available at for the remainder of the SOLPEX operational period. Also, I just emailed Dave Naftz to determine the status of the new USGS buoy which gives a profile of lake temperature, I'll report back when I hear from him.

  4. Excellent. I wondered where these images went. Do you have a lake-mean temperature as well (yes, I always have to keep pushing :-).

    One interesting aspect of these images is how cold the near-shore water is. I wonder if this is related to the shallow lens-like nature of the water there or possible contamination from the exposed land surface. Are these all night/morning overpasses?

  5. I'll work on getting mean temperature from the deep regions of the lake output with the images next week. The temperature gradient between shallow and deep water will continue to become more pronounced through mid-November according to our climatology. When the lake is low the shallows cool off very rapidly in the fall, possibly decreasing the area of "warm water" that is available to set up the lake-700 mb temperature difference that is a necessary condition for lake-effect.

  6. Thanks "MODISman." A strip of warm air down the lake axis is good enough for me!

  7. Also of interest, I have an algorithm that gives GSL temperature as a function of climo and the 7-day average temperature at KSLC here:

    Below the estimated temperature are the 700-mb conditions and lake-effect probability (a work-in-progress) from GFS and NAM BUFR data.